Pressure measurement evaluation and accuracy validation: the Gabarith test

Abstract

Objective: The dynamic distortion introduced by manometric systems has been known for many years, with several methods developed to describe and quantify the degree of distortion. We developed the Gabarith as a technique to describe more accurately, and yet more simply, the dynamic accuracy of the chain of monitoring.

Setting: A pressure monitoring system transforms some input signal, i.e. the actual pressure waveform present in the artery, into some other shape of waveform, i.e. the waveform displayed on the patient monitor. This transformation is characterized by the transfer function of the total system. A complete technique to define the transfer function is to measure the response directly at many different frequencies and combine them to produce the dynamic response plot.

Method: We described the dynamic response of a monitoring chain and we simplified the communication of this dynamic response to users by developing the Gabarith, as a tolerance envelope based on the frequency content of typical pressure waveforms. If a given monitoring chain's dynamic response (including a catheter, a pressure kit and a monitor) can be shown to fall within that tolerance envelope, the chain will provide adequate dynamic accuracy.

Conclusion: "Gabarith tested" means that a pressure kit, in combination with a catheter and a monitor, has had its frequency response function measured and that the function falls within a tolerance band for dynamic accuracy. Passing a Gabarith means that a given level of accuracy will be reached when using the sets which have passed the corresponding test.